BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:The open/closed field line boundary in the ionosphere as a diagnos tic of magnetospheric dynamics - Peter Boakes\, Department of Physics and Astronomy\, University of Leicester DTSTART:20080501T090000Z DTEND:20080501T100000Z UID:TALK11913@talks.cam.ac.uk CONTACT:Christian Franzke DESCRIPTION:The accurate determination of the open/closed field line bound ary\nin the ionosphere is important for quantifying the open magnetic flux \ncontent of the magnetosphere\, a diagnostic of magnetospheric dynamics. We\npresent a statistical comparison of the latitude of the open/closed fi eld\nline boundary (OCB) as estimated by the three different wavelength FU V\ncameras onboard the IMAGE spacecraft and from particle precipitation\nb oundaries from the DMSP satellite. The latitude differences between the\nt hree FUV OCB proxies is less than a degree except in the predawn sector\nw here the electron aurora is found up to two degrees equatorward of the\npr oton aurora and vice versa in the evening sector. Systematic differences\n are found between DMSP and FUV OCB proxies\, which may be used to correct FUV\nOCB proxies to give a more accurate estimation of the OCB.\n\nUsing a uroral images from the IMAGE Wideband Imaging Camera\, we are able to\nmak e an accurate global estimation of the latitude of the OCB and hence\nquan tify the amount of open magnetic flux in the magnetosphere. Making use\nof the Frey substorm database we compare a parent distribution of the\navera ge open magnetic flux content of the magnetosphere\, calculated from\nover 22000 auroral images\, with the open magnetic flux at the time of\nsubsto rm onset\, showing that substorms occur in the upper quartile of the\npare nt distribution and supporting the view that the magnetosphere must be\npr eloaded with open magnetic flux as a necessary condition for substorm\nons et. LOCATION:British Antarctic Survey\, Room 187 END:VEVENT END:VCALENDAR